1. Field of the Invention
The present invention relates to a method and apparatus for transferring eggs from an egg-tray conveyor to a roller conveyor, preferably a roller conveyor oriented perpendicular to the direction of the egg-tray conveyor. The invention uses a plurality of egg-transfer mechanisms, each mechanism including a loader arm and one or more loader heads. The egg-transfer mechanisms can alternate or can operate in tandem. The present invention allows egg to be transferred from the egg tray conveyor to the roller conveyor at speeds that are greatly increased over prior art egg-transfer mechanisms, without increasing the risk that eggs will be damaged during transfer.
2. Description of the Related Art
Prior art large-scale egg-grading machines generally contain stations for washing, candling, weighing and/or sorting eggs. An example of such a machine is shown in U.S. Pat. No. 4,569,444. The eggs in such a prior art egg-grading machine are initially conveyed by a roller conveyor to the various stations in the egg-grading machine.
The eggs which are processed by the above-described prior art egg-grading machine are generally brought to the egg-grading machine in stacked trays containing, e.g., 30 eggs per tray. The trays are initially conveyed to the egg-grading machine as a stack of trays, either in boxes or after removal of the stack from boxes. The stacks of trays are then unstacked by a unstacking machine, such as the machine shown in U.S. Pat. No. 4,355,936. This type of machine unstacks the stacks of trays, and places individual trays on a conveyor. The conveyor then conveys the trays in one or more rows to a transfer station. At the transfer station, a transfer mechanism removes the eggs from the egg trays and transfers the eggs to the roller conveyor of the egg-grading machine.
U.S. Pat. No. 3,587,888 shows a prior art mechanism for transferring from an egg-tray conveyor to a roller conveyor of an egg-grading machine. In this type of device, the transfer mechanism uses two or more loader heads with vacuum grippers which grasp the eggs on the egg trays from above and transfer the eggs in groups to the roller conveyor. The roller conveyor is generally perpendicular to the egg-tray conveyor. This type of prior art transfer mechanism uses a single loader arm with two or more loader heads, each loader head containing an array of vacuum grippers to thereby remove eggs from two or more trays simultaneously. The loader head swings away from the egg-tray conveyor after gripping the eggs in the egg trays, and then deposits the gripped eggs onto the roller conveyor. Such an arrangement has inherent speed limitations, as the single loader arm can only be operated at a certain optimal speed before there is a risk of damaging eggs during transfer. As a result, the total speed of the egg-grading system can be limited by the speed at which the transfer mechanism can be optimally operated.